1. Field of the Invention
The present invention relates to a portable trimmer such as a hanging-type trimmer, a hedge trimmer, or the like wherein power generated by an internal combustion engine is generally transmitted through a centrifugal clutch to a rotatable cutter and, in particular, it relates to a portable trimmer which is equipped with a brake device to prevent unexpected operation of the rotatable cutter.
2. Description of the Related Art
In a portable trimmer such as a hanging type trimmer, a backpack type trimmer, a hedge trimmer, or the like, a driving mechanism which transmits the power generated by an internal combustion engine through a centrifugal clutch to a rotatable cutter is generally employed. In these types of portable trimmers, it is known to include a brake device in which the rotation of a clutch drum is forcibly restricted when, for example, the trimmer is placed on the ground or a flat floor. In this way start up of the trimmer is restricted or the trimming operation is temporarily stopped. The unexpected rotation of the rotatable cutter which is mechanically connected to the clutch drum is restricted by a band brake wound around the centrifugal clutch (see Japanese Patent Public Disclosure No. Sho 40-28526).
The afore-mentioned conventional brake device has a stand which is provided in the vicinity of the centrifugal clutch. The stand moves a predetermined stroke in an upward direction by its own weight of the internal combustion engine when the portable trimmer is placed on the ground. It also has an operating rod to which a free end of the band brake is connected. The operating rod engages with a pin fixed to the stand whereby it swings when the stand moves in the upward direction. It causes the band brake to be tightened to prevent the clutch drum from being rotated. This type of brake device is effective to prevent the unexpected rotation of the rotatable cutter while the trimmer is placed on the ground. The safety during the start-up time is effectively improved thereby.
However, in the afore-mentioned conventional brake device, the braking and releasing of the clutch drum relies on motions such as placing the portable trimmer on the ground or lifting it therefrom. Therefore, there is a possibility that the rotatable cutter may suddenly start rotating when the trimmer is lifted especially in the case of a cold start-up where a throttle is set to be wide open for relatively high engine revolution.
Therefore, it is an object of the present invention to provide a portable trimmer having a brake device which enhances and improves the conventional safety level of the rotatable cutter.